TW201722557A - Preparation method of composite selective catalytic reduction catalyst - Google Patents

Abstract

The preparation method of the composite selective catalytic reduction catalyst comprises the following steps. The first metal compound support, the second metal compound, the third metal compound, and water are mixed to form a precursor solution. The precursor solution is formed into a dry powder of the mixture by a spray drying process. The dry powder of the mixture is subjected to a calcination process.

Description

Preparation method of composite selective catalytic reduction catalyst

The invention relates to a method for preparing a catalyst, and in particular to a method for preparing a composite selective catalytic reduction catalyst.

In general, selective catalytic reduction (SCR) catalyst manufacturing techniques include coprecipitation, sol-gel, wet impregnation, and chemical vapor deposition. Among them, the coprecipitation method is a method of preparing a powder in a liquid phase which is most commonly used, and therefore, this method is industrially used to produce a large amount of powder. In the chemical precipitation method, one or more solvents are selected, and the desired components are dissolved in a solvent and stirred at an appropriate concentration, pressure, temperature, and fixed pH, so that the reactants are present in the solution in the form of a scorpion. Then, the mixed solution is added to a precipitating agent (for example, sodium carbonate, ammonia water), and adjusted to an appropriate pH to precipitate the cation in the solution in a saturated state. If there are more than one type of Yangzizi, and these cations will precipitate ruthenium at the same time or in the same time when the precipitant is added, this phenomenon is called coprecipitation. pH is an important reaction in the chemical coprecipitation process. The coprecipitation method has the advantages of being simple and easy to operate, but having disadvantages such as low purity, large particle radius, difficulty in dispersion, and inability to continuously produce, and is suitable for preparing an oxide.

The sol-gel method is based on an inorganic polymerization reaction to prepare an inorganic polymer compound in which a metal alkoxide or an inorganic metal compound is used as a precursor, water is used as a hydrolyzing agent, and an alcohol is used as a solvent. In the solution, the precursor undergoes hydrolysis and condensation to form fine particles, and then becomes a sol which allows the fine particles to continue to react and bond together, and then solidifies the sol into a gel. The sol-gel method has the advantages of many reaction species, uniform product particles, easy process control and good particle dispersibility, but has the disadvantages that the particle size is difficult to control and cannot be continuously produced.

The impregnation method is to dissolve the metal precursor in a specific solution, mix the carrier with the solution, and then dry and calcin the carrier to complete the preparation of the catalyst, wherein the drying temperature, the solution concentration and the solution during the contact of the carrier Conditions such as stirring will affect the activity of the catalyst. The advantage of the impregnation method is that the process is simple, but has the disadvantages of dispersibility, poor purity, and inability to continuously produce. The chemical vapor deposition method utilizes a chemical reaction of a metal compound in a vapor phase, and forms a nanoparticle through a nuclear condensation and condensation process. The advantages of the chemical vapor deposition method are high purity of the product, uniform particle size distribution, and continuous production in the gas phase, but the disadvantages are that the precursors are mostly expensive and environmentally harmful compounds such as organometallic chlorides or alkoxides.

The invention provides a preparation method of a composite selective catalytic reduction catalyst, which has an operation procedure which is simple, rapid and continuously produced.

The preparation method of the composite selective catalytic reduction catalyst of the present invention comprises the following steps. The first metal compound support, the second metal compound, the third metal compound, and water are mixed to form a precursor solution. The precursor solution is formed into a dry powder of the mixture by a spray drying process. The dry powder of the mixture is subjected to a calcination process.

In an embodiment of the invention, the composite selective catalytic reduction catalyst comprises a manganese-iron-titanium composite selective catalytic reduction catalyst.

In an embodiment of the invention, the first metal compound carrier includes a titanium oxide support.

In an embodiment of the invention, the titanium oxide support comprises titanium hydroxide.

In an embodiment of the invention, the method for forming the titanium oxide support includes mixing water, a titanium oxide hydrated precursor, and ammonia water.

In an embodiment of the invention, the second metal compound comprises a manganese metal compound.

In an embodiment of the invention, the manganese metal compound comprises manganese acetate.

In an embodiment of the invention, the third metal compound includes an iron metal compound.

In an embodiment of the invention, the iron metal compound comprises iron nitrate.

In an embodiment of the invention, the spray drying process includes a spray drying process using a spray drying apparatus including a nozzle, a reaction chamber, a particulate collector, and a sample collection bottle.

In an embodiment of the invention, the nozzle is used to atomize the precursor solution into the reaction chamber.

In an embodiment of the invention, the carrier gas is further introduced into the spray drying device for carrying the atomized precursor solution.

In an embodiment of the invention, the carrier gas is compressed air.

In an embodiment of the invention, the spray drying device has a spray air pressure of about 3-5 kg/cm 2 .

In an embodiment of the invention, the spray drying device has an inlet temperature of about 150-300 °C.

In an embodiment of the invention, the spray drying device has an outlet temperature of about 105-150 °C.

In an embodiment of the invention, the nozzle is fed at a rate of from about 2 to about 5 grams per minute.

In an embodiment of the invention, the ratio of solids to water in the precursor solution is about 1:10.

In an embodiment of the invention, the temperature of the calcination process described above is about 350 °C.

In one embodiment of the invention, the composite selective catalytic reduction catalyst described above has a size of from about 0.5 to about 3 microns and a specific surface area of from about 52 to about 74 square meters per gram.

Based on the above, the present invention employs a spray drying process to produce a composite selective catalytic reduction catalyst having an operating procedure that is simple, rapid, and continuously produced. In this way, it is possible to avoid the problem that the particle size unevenness, poor dispersibility, or continuous generation may occur in the general composite type selective catalytic reduction catalyst process.

The above described features and advantages of the invention will be apparent from the following description.

1 is a schematic diagram of a spray dryer for a method of preparing a composite selective catalytic reduction catalyst, in accordance with an embodiment of the present invention. In the present embodiment, first, the first metal compound carrier, the second metal compound, the third metal compound, and water are mixed to form a precursor solution PS. In the SCR catalyst process, the first metal compound support is, for example, a support such as a titanium oxide support, a ruthenium oxide support or an alumina support. In the present embodiment, a titanium oxide support of titanium hydroxide is used. In the present embodiment, the method for producing the titanium oxide support is, for example, uniformly stirring and mixing the powder of titanium metal hydrate, water, and ammonia water at normal temperature and pressure to form a titanium oxide precipitate, followed by evacuating the titanium oxide precipitate. The filtration method and deionized water were washed several times to obtain a titanium oxide support. In the present embodiment, the titanium metal hydrate is, for example, titanium oxide hydrate (TiO(OH) ₂ ). In the SCR catalyst process, the second metal compound includes a metal compound such as a manganese metal compound, cerium oxide or vanadium oxide. In the present embodiment, manganese acetate is used as the second metal compound, and its concentration is, for example, 5% by weight to 30% by weight, such as 5% by weight, 10% by weight, 15% by weight, 20% by weight, 25% by weight or 30% by weight. %. In the SCR catalyst process, the third metal compound includes a metal compound such as an iron metal compound, cobalt oxide, or nickel oxide, or a noble metal such as gold or silver. In the present embodiment, iron nitrate is used as the third metal compound, and its concentration is, for example, 5% by weight to 20% by weight, such as 5% by weight, 10% by weight, 15% by weight or 20% by weight. In this embodiment, the water is, for example, deionized water. In the present embodiment, for example, the first metal compound carrier, the second metal compound, the third metal compound, and water are uniformly stirred and mixed at normal temperature to form a precursor solution PS. In the present embodiment, the precursor solution PS is, for example, an Mn-Fe-Ti acidic aqueous solution. In the present embodiment, the ratio of the solid content to the water in the precursor solution PS is, for example, about 1:10, that is, the ratio of the first metal compound carrier, the second metal compound, and the third metal compound to water, for example, It is about 1:10.

Referring to FIG. 1, next, the precursor solution PS is formed into a mixture dry powder DP by a spray drying process. In the present embodiment, the spray drying process is performed, for example, in the spray drying apparatus 100, which includes, for example, a nozzle 110, a reaction chamber 120, a particulate collector 130, and a sample collection bottle 140. In detail, the precursor solution PS is sent to the nozzle 110, and the nozzle 110 atomizes the precursor solution PS and sprays it into the reaction chamber 120 to form a mixture dry powder DP in the reaction chamber 120. In the present embodiment, the liquid feeding speed of the nozzle 110 is, for example, about 2 to 5 g/min. In the present embodiment, the spray air pressure of the nozzle 110 is, for example, about 3-5 kg/cm 2 . In the present embodiment, the carrier gas CG continuously flows into and out of the spray drying device 100 to carry the atomized precursor solution PS. In the present embodiment, the carrier gas CG is, for example, compressed air. In the present embodiment, the reaction chamber 120 has, for example, high temperature energy such that the mixture dry powder DP reacts in the reaction chamber 120. In the present embodiment, the inlet temperature of the reaction chamber 120 of the spray drying apparatus 100 is, for example, about 150 ° C to 300 ° C, and the outlet temperature of the spray drying apparatus 100 is, for example, about 105 ° C to 150 ° C. That is, the temperature at which the atomized precursor solution PS enters the reaction chamber 120 is, for example, about 150 ° C to 300 ° C, and the temperature of the formed dry powder DP leaving the reaction chamber 120 is, for example, about 150 ° C - 300. °C. In the present embodiment, the carrier gas CG is, for example, heated compressed air, thereby providing the high temperature energy required for the reaction chamber 120 by passing the carrier gas CG into the reaction chamber 120. In the present embodiment, the resulting material after the reaction is collected in the sample collection bottle 140 by the particle collector 130. In the present embodiment, the particulate collector 130 is, for example, a bag dust collector, an electrostatic precipitator or a cyclone. The sample collection bottle 140 is, for example, a stainless steel container. In the present embodiment, the mixture dry powder DP is, for example, a Mn-Fe-Ti composite type material which is a nanoparticle having a uniform particle size.

Then, the mixture dried powder DP is subjected to a calcination process to form a composite selective catalytic reduction catalyst powder. In the present embodiment, the calcination process is carried out, for example, in a high temperature furnace. In the present embodiment, the temperature of the calcination process is, for example, about 350 ° C to 550 ° C, and the time of the calcination process is, for example, about 4 to 6 hours. In the present embodiment, the temperature of the calcination process is, for example, about 350 ° C, and the time of the calcination process is, for example, about 6 hours. In the present embodiment, the composite selective catalytic reduction catalyst is, for example, a Mn-Fe-Ti composite type selective catalytic reduction catalyst, which is, for example, Mn ₂₀ Fe ₁₀ -TiO ₂ . In the present embodiment, the composite selective catalytic reduction catalyst powder formed has a size of, for example, about 0.5 to 3 μm, and a specific surface area of, for example, about 52 to 74 m 2 /g.

In the present embodiment, the preparation method of the composite selective catalytic reduction catalyst is carried out by a rapid spray drying technique without requiring a cumbersome and time consuming preparation process. In detail, the water can be quickly evaporated by spraying the first metal compound monomer, the second metal compound, and the third metal compound precursor into a droplet at a high pressure and passing into the heated reaction chamber. To leave a dry solid powder and then separate the solid powder from the gas stream. Therefore, the preparation method of the composite selective catalytic reduction catalyst has the advantages of simple, rapid, continuous production, low cost, and the like, and has mass production potential. In the present embodiment, the Mn-Fe-Ti composite type selective catalytic reduction catalyst has good removal efficiency for nitrogen oxides at low temperature, and the Mn-Fe-Ti composite catalyst can be applied to the end of exhaust gas in the future. (eg, emissions from exhaust gases from steel or semiconductor plants), such as volatile organic compounds (such as acetone and toluene), and other multi-functional reductions in air pollutants. In addition, the preparation method of the composite selective catalytic reduction catalyst of the present embodiment can be applied to industries such as the pharmaceutical industry, the cosmetics industry, the solar energy industry, the gas sensor, the micro-electromechanical, the printing industry, the dye pigment industry, etc. Catalysts, pharmaceuticals (directing agents), cosmetics, high-intensity color pigments, super-tough ceramic materials and other products.

Next, the characteristics of the composite selective catalytic reduction catalyst produced by the method for producing a composite selective catalytic reduction catalyst of the present invention will be described by way of experimental examples and comparative examples.

[Experimental example]

Method for preparing titanium oxide support

First, a powder of titanium oxide hydrate (TiO(OH) ₂ ), water, and ammonia water are stirred and mixed at normal temperature and normal pressure to form a titanium oxide precipitate. Next, the titanium oxide precipitate was subjected to suction filtration and deionized water washing several times to obtain a titanium oxide support.

Manganese iron oxide is coated on the titanium oxide support by a spray drying process

First, the washed titanium oxide support and different concentrations of manganese acetate aqueous solution (5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%), different concentrations of ferric nitrate aqueous solution (5 wt%, 10 wt%, 15 wt%) %, 20 wt%) and a deionized aqueous solution were mixed so that the solid to liquid ratio was 1:10. Next, the above mixed liquid was uniformly stirred to form a precursor solution. Then, the precursor solution is atomized through a nozzle of the spray drying device to spray the precursor solution into the reaction chamber, wherein compressed air is used as a carrier gas, and the carrier gas is heated to pass into the reaction chamber. The desired high temperature energy is supplied to the reaction chamber after the chamber. The material produced after the reaction in the reaction chamber is then collected in a sample collection bottle using a pellet collector. Next, the collected powder was placed in a high temperature furnace and calcined at 350 ° C for 6 hours.

[Comparative Example 1]

A Mn-Fe-Ti composite catalyst having the same ratio of titanium, manganese and iron as the product obtained in the experimental example was prepared by a coprecipitation method.

[Comparative Example 2]

A Mn-Fe-Ti composite catalyst having the same ratio of titanium, manganese and iron as the product obtained in the experimental example was prepared by a wet impregnation method.

[Comparative Example 3]

A Mn-Fe-Ti composite catalyst having the same ratio of titanium, manganese and iron as the product obtained in the experimental example was prepared by a sol-gel method.

[NO removal rate of Mn-Fe-Ti composite catalyst]

Selective catalytic reduction tests were carried out on the Mn-Fe-Ti composite catalysts obtained in the experimental examples and Comparative Examples 1 to 3, respectively. The test conditions included: NO (500 ppm), NH ₃ (500 ppm), O ₂ (5). %), space flow rate (50000 h ^-1 ) and reaction temperature (100 ° C), the test results are shown in Figure 2.

2, when the operating temperature is 100 ° C, the removal rate of nitrogen oxide by the Mn-Fe-Ti composite catalyst prepared by the spray drying method of the experimental example of the present invention can reach about 99%, and the comparative example 3 is used. The removal rate of nitrogen oxide by the Mn-Fe-Ti composite catalyst prepared by the sol-gel method was about 91%, and the Mn-prepared by the wet impregnation method of Comparative Example 2 and the coprecipitation method of Comparative Example 1 was used. The removal rate of nitrogen oxide by Fe-Ti composite catalyst was only 89% and 83%, respectively. From this, it is understood that the Mn-Fe-Ti composite catalyst prepared by the spray drying method of the experimental example of the present invention has a remarkably high nitrogen oxide removal rate. That is to say, the Mn-Fe-Ti composite type catalyst prepared by the spray drying method of the experimental example of the present invention has a better nitrogen oxide removal rate than the other conventional methods.

In addition, the above experimental examples were compared with the catalysts published by the F. Liu research team in 2009 and 2014. The comparison results are shown in Figure 3, in which the catalyst was published by Liu et al. in 2009 (in Figure 3 "Liu et al., 2009" is a MnFe-TiO ₂ catalyst prepared by a precipitation method, and the catalyst published by Liu et al. in 2014 (indicated by "Liu et al., 2014" in Fig. 3) is The MnWO _x pure metal catalyst prepared by the precipitation method (which does not have a support), and the experimental conditions of the present invention and the catalysts disclosed by Liu et al. are all operating conditions of NO (500 ppm) and NH ₃ (500 ppm). ), O ₂ (5%), space flow rate (50000 h ^-1 ), and reaction temperature (100 ° C). In particular, the F. Liu research team has published 28 journals on SCR denitrification catalysts since 2008, and all of its SCR journals have been cited more than 500 times, both in terms of quality and quantity. Level, its paper can be said to be an important indicator of SCR catalyst.

It can be seen from Fig. 3 that the SCR denitration efficiency of the MnFe-TiO ₂ catalyst prepared by Liu et al. in the low temperature section (such as 75 ° C - 125 ° C) cannot reach 80%, but can reach 80% after 150 ° C. SCR denitration efficiency. On the other hand, the MnWO _x pure metal catalyst prepared by Liu et al. can achieve nearly 100% denitration efficiency at 75 ° C, but the metal catalyst will gradually gradually in the high temperature section (200 ° C - 300 ° C). Inactivated, its SCR denitration efficiency drops to 60% at 300 °C. The denitration efficiency of the Mn ₂₀ Fe ₁₀ -TiO ₂ catalyst of the experimental example of the present invention at low temperature is similar to the denitration efficiency of the MnWO _x pure metal catalyst prepared by Liu et al., and the SCR denitration efficiency at 80 ° C Also up to 92%, in addition, the Mn ₂₀ Fe ₁₀ -TiO ₂ catalyst of the experimental example of the present invention can maintain a denitration efficiency of up to 98% over the entire temperature range of 100 ° C to 300 ° C. It can be seen that the catalyst of the experimental example of the present invention is superior to the catalyst of the F. Liu research team in terms of denitration efficiency and operating temperature range.

In summary, the preparation method of the composite selective catalytic reduction catalyst of the present invention is carried out by a rapid spray drying technique without requiring a cumbersome and time-consuming preparation process. In detail, the first metal, the second metal and the third metal precursor solution are sprayed into a droplet at a high pressure and passed into a heated reaction chamber so that the moisture can be quickly evaporated to leave a dry The mixture is solid powder and the mixture solid powder is then separated from the gas stream. Thereafter, the mixture solid powder is calcined to form a composite selective catalytic reduction catalyst powder. Therefore, the preparation method of the composite selective catalytic reduction catalyst has the advantages of simple, rapid, continuous production, low cost, and the like, and has mass production potential. In addition, the composite selective catalytic reduction catalyst produced by the spray drying technique of the present invention is compared to a composite selective catalytic reduction catalyst produced by a conventional method such as a coprecipitation method, a wet impregnation method, or a sol-gel method. It has better efficiency.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧ spray drying device
110‧‧‧ nozzle
120‧‧‧Reaction chamber
130‧‧‧Particle collector
140‧‧‧ Sample collection bottle
DP‧‧‧ mixture dry powder
PS‧‧‧Precursor solution

1 is a schematic diagram of a spray dryer for a method of preparing a composite selective catalytic reduction catalyst, in accordance with an embodiment of the present invention. Fig. 2 is a bar graph showing the results of a selective catalytic reduction test of the Mn-Fe-Ti composite catalyst obtained in the experimental examples of the present invention and Comparative Examples 1 to 3. Fig. 3 is a line graph showing the selective catalytic reduction denitration efficiency of a catalyst of the Mn-Fe-Ti composite catalyst of the experimental example of the present invention and Liu et al., published in 2009 and 2014.

Claims (20)

A method for preparing a composite selective catalytic reduction catalyst comprises: mixing a first metal compound carrier, a second metal compound, a third metal compound and water to form a precursor solution; drying by spraying The process is such that the precursor solution forms a dry powder of the mixture; and the dry powder of the mixture is subjected to a calcination process. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the composite selective catalytic reduction catalyst comprises a manganese-iron-titanium composite selective catalytic reduction catalyst. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the first metal compound support comprises a titanium oxide support. The method for producing a composite selective catalytic reduction catalyst according to claim 3, wherein the titanium oxide support comprises titanium hydroxide. The method for preparing a composite selective catalytic reduction catalyst according to claim 3, wherein the method for forming the titanium oxide support comprises mixing water, a titanium oxide hydrated precursor, and ammonia water. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the second metal compound comprises a manganese metal compound. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the second metal compound comprises manganese acetate. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the third metal compound comprises an iron metal compound. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the third metal compound comprises iron nitrate. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, comprising performing the spray drying process using a spray drying device, the spray drying device comprising a nozzle, a reaction chamber, and a particle A collector and a sample collection bottle. The method for preparing a composite selective catalytic reduction catalyst according to claim 10, wherein the nozzle is used to atomize the precursor solution into the reaction chamber. The method for preparing a composite selective catalytic reduction catalyst according to claim 11, further comprising introducing a carrier gas into the spray drying device for carrying the atomized precursor solution. The method for preparing a composite selective catalytic reduction catalyst according to claim 12, wherein the carrier gas comprises a compressed air. The method for preparing a composite selective catalytic reduction catalyst according to claim 11, wherein the spray drying device has a spray air pressure of about 3-5 kg/cm 2 . The method for preparing a composite selective catalytic reduction catalyst according to claim 10, wherein the reaction chamber has an inlet temperature of about 150 to 300 °C. The method for preparing a composite selective catalytic reduction catalyst according to claim 10, wherein the reaction chamber has an outlet temperature of about 105 to 150 °C. The method for preparing a composite selective catalytic reduction catalyst according to claim 10, wherein the nozzle is fed at a rate of about 2 to 5 g/min. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the ratio of the solid content to the water in the precursor solution is about 1:10. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the temperature of the calcination process is about 350 °C. The method for preparing a composite selective catalytic reduction catalyst according to claim 1, wherein the composite selective catalytic reduction catalyst has a size of about 0.5 to 3 μm and a specific surface area of about 52 to 74 square. Metric / gram.